Jessica Gradillas and her doe-eyed horse, Loki, have taken a lot of high jumps together, but the hurdle they’re approaching now threatens to separate the devoted pair.

A small run of bad luck has put Gradillas, a 20-year-old student and expert equestrian, into a financial hard spot that might mean she can’t afford to keep the fog-grey horse she hopes to ride to a future Olympic medal.

“If I can’t pay for board and to feed him, (selling him) is probably the best thing for the horse, but it’s the last thing I want to do,” she said. “He’s dripping in talent and has the potential to go all the way. (But) he’d be better off elsewhere if I can’t find some way to fix this.”

Always athletic, Gradillas, who lives in Hayward and boards Loki in Livermore, took her first riding lesson 10 years ago — a gift from the women in her family. A naturally talented rider, she eventually began training in the very difficult — and expensive — sport of eventing. It requires horse and rider to compete in three different disciplines: dressage, in which horse and rider perform a series of intricate movements; stadium jumping in an arena; and cross country, in which horse and rider traverse a large open field course featuring water obstacles, ditches, steep banks and downed logs. The competition normally takes place over three days.

“I tell everyone that it’s the horse version of a human triathlon,” Gradillas said. “It’s extremely strenuous for the horses, who have to be in great shape.” For talented horse-and-rider teams like Gradillas and Loki, a 6-year-old Holsteiner gelding, the road to the top echelon is an expensive one, paved with competition entry fees, boarding bills, training for horse and rider, transport and shipping to competitions and veterinary care. Until recently, Gradillas made ends meet with a multipronged support system — her own paycheck, and, as is common in the eventing world, a bit of support from others. In her case, that included some funding from her supportive grandmother, a close family friend, and an equestrian acquaintance who contributed to Loki’s support in exchange for the occasional riding session.

That arrangement fell into disarray recently. Gradillas, who works at Kaiser Permanente as a medical assistant, is also in school to become a medical ultrasonagrapher and is thus unable to generate a full-time income. The woman who occasionally rode Loki developed health problems that prohibited her from riding, so she withdrew her financial support. Gradillas’ grandmother, Chris Johnson, also is also battling health issues and is unable to contribute as she has in the past.

“The family has helped her as much as we can,” Johnson said. “And through all of this stuff that goes on, she continues to work.”

Until Gradillas graduates from school and can work full-time, the pair’s future is in question — a painful situation for their trainer, Ann Byron, who sees potential greatness in their future.

“They’re both very talented … with every step they’re only getting better,” she said. “I think Jess would like to represent the U.S. in the future, which means she has to get to the big competitions. Loki’s a young horse — up-and coming. She needs to find a way to close the (financial) gap; to find sponsors who believe in her and will stand behind her and her horse as she moves up these levels.” As for Gradillas, she can’t imagine having to lose her four-legged training partner.

“He’s my best friend,” she said. “I’ve never been attached to a horse like I am with him. He’d do anything for me, and I’m trying to do everything for him.”

Longtime family friend Chris Jewell, who contributes to the team’s upkeep but can’t afford more, is hoping private or business sponsors might help fill the gap — just for a while.

“She’s just this amazing kid,” she said. “She’s very well intentioned and very focused to achieve a dream she had at 7 years old. She’d doing everything she knows to do to keep that dream alive, and now she’s needing help.”